Steganography with photo-responsive dyes

ABSTRACT

An article identifier or code including at least one photo-responsive dye and a method of encoding or embedding information in same. A reader device for decoding or extracting information in an article identifier or code and verifying or authenticating that information and the associated extraction and authentication methods.

BACKGROUND OF THE INVENTION

In the field of inks and dyes, there are several applications forfluorescent inks and dyes and combinations of florescent inks and dyeshaving disparate or complementary frequency responses. Various securityand anti-tamper and authentication solutions making use of fluorescentor otherwise photo-responsive inks are currently known, but they havedeficiencies that enable them to be readily counterfeited or otherwisecircumvented. Fluorescent or similarly photo-responsive dyes aretypically used so that the photo responses of the dyes do not overlap orare otherwise readily visibly distinguishable during simultaneous orsingle-source illumination. It would be a significant advantage,however, to leverage multiple photo-responsive materials to create avisible code that used sequential or modulated illumination, multipleillumination sources, and/or forms of spectral filtering to add furtherlayers of security and authentication to the code.

INVENTION SUMMARY

Aspects of the present invention are directed to photo-responsive,dye-based article identifiers that identify some characteristic or traitof an article, methods of producing those identifiers, readers to readthe information stored in such identifiers, and methods of reading andverifying the information stored in such identifiers.

Embodiments of article identifiers may include dye-based identifiersthat include two or more fluorescent dyes having overlapping responsefrequency bands or a common response or excitation frequency band. Insome embodiments, the response and/or excitation frequency bands of dyesin a multiple-dye identifier may be the same. In other embodiments, theresponse and/or excitation frequency band of one dye may be containedwithin the response frequency band of a second dye. In yet furtherembodiments, spectrally similar dyes (ones whose response frequencybands are not readily distinguishable) may include other differingcharacteristics such as different fluorescence response delays,differing excitation frequency bands, or different post-fluorescencerelaxation times.

In some embodiments, part of the information contained in the identifiermay be defined or accessed by manipulating or otherwise knowing thedifference between the frequency bands of the response or excitationfrequency bands of two or more dyes. Such embodiments may includevariations where a dye with a narrow-spectrum response frequency band iscombined or otherwise utilized along with a dye with a broad-spectrumresponse that includes the narrow-spectrum response band. Alternateembodiments may include variations where a dye with a narrow-spectrumexcitation frequency band is combined or otherwise utilized along with adye with a broad-spectrum excitation band that includes thenarrow-spectrum excitation band.

Further embodiments may take advantage of relaxation/response timeprofiles of dyes through the use of modulated illumination or sequentialillumination for excitation. In such embodiments, two dyes havingsimilar or, in some cases, identical excitation or response bands mayhave different relaxation/recovery times associated with anexcitation/response cycle. Modulated illumination and detection mayallow a reader device to distinguish one dye from another based onresponse times. In alternate embodiments, sequential illumination mayallow for differentiation between narrow-band and wide-band excitationor response bands and/or may allow for differentiation between dyeshaving the same response or excitation bands or that are physicallyoverlapping in an image or code.

Embodiments of the invention may also include a reader device configuredto read and authenticate or verify a printed code containing at leastone photo-responsive dye. Embodiments of such reader devices may includeone or more electro-optical (EO) radiation emitters that emit radiationassociated with excitation frequency band(s) of the fluorescent orotherwise photo-responsive dye(s). Embodiments of emitters may emitvisible-spectrum EO radiation or may emit infra-red, ultra-violet,millimeter-wave or some combination thereof. Embodiments of emitters mayemit modulated illumination pulses or may have a specific emissionsequence.

Embodiments of a reader device may also include a detector that detectsthe response of one or more fluorescent dyes. Detector embodiments mayalso include imaging detectors or detector components that image theprinted code in a non-illuminated and/or partially illuminated statethat may be associated with sequential or modulated emitter operation orotherwise based on the excitation/response times associated with one ormore of the dyes in the code.

Embodiments of a reader device may have one or more processors andmemory storage areas for control of the emitter(s) and detector(s) aswell as processing storage of detection results. Embodiments ofprocessors and memory may include custom-built digital data processingand storage components or commercially available components.Embodiments, of processors and data storage media may be magnetic,optical, electronic, or some combination thereof.

Embodiments of a reader device may also include an interface and/or dataconnection/output points that allow a user or downstream system tointeract with the reader device. Embodiments may include keypad ortouch-screen interfaces, displays, infra-red ports, Ethernet ports,sockets for removable storage media, and/or custom-designed interfacesand/or data access points. Further embodiments of a reader device mayinclude a system bus or other interconnection system or device allowingthe various components of the reader to communicate through one or morecommon data channels.

Embodiments of the invention may also pertain to methods of encoding orstoring information in article identifiers of the type discussed above,and of recovering or authenticating the data stored, encoded, orembedded in such an embodiment of an article identifier.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein

FIG. 1 a depicts an embodiment of a reader device according to thepresent invention reading an article identifier according to the presentinvention;

FIG. 1 b depicts an embodiment of a reader device according to thepresent invention;

FIG. 2 a depicts an embodiment of an alphanumeric article identifieraccording to the present invention;

FIG. 2 b depicts an embodiment of a partially alphanumeric articleidentifier according to the present invention;

FIG. 2 c depicts an embodiment of an article identifier according to thepresent invention;

FIG. 2 d depicts an embodiment of an article identifier according to thepresent invention;

FIG. 2 e depicts an embodiment of an article identifier according to thepresent invention;

FIG. 2 f depicts an embodiment of an image-based article identifieraccording to the present invention;

FIG. 3 depicts an embodiment of an article equipped with an articleidentifier according to the present invention;

FIG. 4 depicts an embodiment of a reader device according to the presentinvention; and

FIG. 5 depicts an embodiment of a reader device and an associated datasystem according to the present invention.

The drawings will be described in detail in the course of the detaileddescription of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of the invention refers to theaccompanying drawings. The same reference numbers in different drawingsidentify the same or similar elements. Also, the following detaileddescription does not limit the invention. Instead, the scope of theinvention is defined by the appended claims and equivalents thereof.

Dyes such as anti-stokes fluorescent dyes, or similar dyes that may beused to produce inks or pigments that are visible but also responsive tophoto-excitation as specific (visible or non-visible) frequencies may beused to generate visible codes that have a secondary, frequency-specificcomponent which may or may not be visible.

In one embodiment, two photo-responsive dyes having the same emissionfrequency but disparate excitation frequencies may be applied to createa visible alpha-numeric, bar-code, two-dimensional image-based code, orthree-dimensional and/or holographic image-based code. Part of the codeprinted in the first dye may require a particular excitation frequency,such as infra-red, ultra violet, or a particular visible-spectrumfrequency, and may generate an electro-optically readable response in aparticular frequency band. The part of the code printed in the seconddye may operate in a similar fashion but with a different excitationfrequency to elicit the response. In some embodiments, the printed codemay also have portions that are readily visible to the naked eye. Inother embodiments, the printed code may be partially or completelyinvisible to the naked eye or otherwise not fully discernible throughvisible-spectrum illumination. Yet further embodiments may employ asingle dye coupled with a visible image or with a textured structuresuch as Braille type, embossed or raised lettering or images, or with athree-dimensional structure such as a crystal or laminated substancehaving one or more photo-responsive materials embedded or includedtherein. Further embodiments still may employ a photo-responsive dye asa code-bearing dye and another, different photo-responsive dye as abackground or a masking/concealing dye. In some embodiments, the maskingdye may have a response frequency band that includes the responsefrequency band of the code-bearing dye. In other embodiments, themasking dye may have an excitation frequency band that includes theexcitation frequency band of the code-bearing dye.

To read embodiments of such codes, a specialized device may be requiredto illuminate the code with the required frequencies (eithersimultaneously, sequentially, or at a specific time frequency, dependingon the particular fluorescent and/or phosphorescent excitation andrelaxation properties; the physical properties of any associatedmaterials or textured surfaces; and material-specific properties of thefluorophore in question) and read the photo-responsive code portions (aswell as the visible portions in cases where some or all of the code isprinted, rendered, or responsive in the visible spectrum). The codereader may the use the code for a variety of authentication orverification routines.

An embodiment of a code reader device is depicted in FIG. 1 a. Theembodiment shown in configured for a code embodiment using twophoto-responsive dyes with different excitation frequency bands and thesame response frequency band. In such an embodiment, a reader device,such as a scanner 1101, may include a user interface 1111, a memoryportion 1151, a processor 1161, an emitter 1131 that emitselectro-optical radiation having a first frequency 1041 and a secondfrequency 1031 corresponding to the excitation frequencies of the dyes,and a detector 1141 that reads the photo-activated response fromilluminated dyes 1001, 1021 contained in a code or article identifier1031 located on an article or article package 1011. The reader device1101 portions may all be connected/interfaced with each-other through asystem bus 1121 or similar information conduit.

Embodiments of the emitter portion 1131 of the reader device may haveone or more electro-optical emitters that emit electro-optical radiation1031, 1041 such as infra-red or ultra-violet lamps or LEDs, lasers,specific visible-spectrum light sources, or any other number ofelectro-optical radiation sources suitable for triggering aphoto-response from one or more photo-responsive inks or dyes. Alternateembodiments may include multiple emitters or may include configurable orswitchable emitters that may have a range of emitted radiationfrequencies or wavelengths to choose from or cycle through on aconfigurable or pre-determined sequence. Further embodiments may includeemitters or emitter components that generate visible-spectrum radiationin particular wavelength ranges associated with specific dye colors. Yetfurther emitter embodiments may include range-finding signal emissioncapabilities for reading raised, embossed, textured, orthree-dimensional code-bearing portions such as Braille, textured ink,raised or engraved lettering or images, and/or code portions embedded intransparent or translucent solids. Yet further emitter embodiments mayinclude laser emitters specifically configured to trigger certain typesor portions of holograms. Further embodiments still may include anemission sequencer or modulator that establishes an emission sequence totrigger one or more dyes in a particular order and/or to generate aparticular response based on expected material-specific fluorescenceresponse times. Such a sequencing or modulation component may be part ofthe emitter 1131 or may be included in an emitter control sequenceperformed by the processor 1161 and/or selectable through the userinterface 1111.

The detector portion 1141 in the embodiment shown is configured todetect the particular electro-optical wavelength(s) 1021 associated withthe response frequency of the dyes in the code or article identifier1031 (such as, for instance, visible spectrum and near infra-red, aparticular set of visible spectrum wavelengths, high-frequency visiblespectrum and ultra-violet, or other combinations thereof). Embodimentsmay be configured to detect and identify or otherwise captureinformation associated with frequency modulations derived frommaterial-specific fluorescence response times. Yet further embodimentsmay be configured to detect range-finding signals or otherwise work withan emitter in a range-finding capacity. Further embodiments still mayinclude detectors that read relative temperature differences or spectralvariations between visually indistinguishable dyes that are notspectrally identical. Embodiments of a detector may include spectrometryor spectrographic capabilities. Other embodiments may include one ormore electro-optical detectors with one or more expected response ordetection profiles stored in the memory 1151 or otherwise provided tothe processor 1161 for comparison, validation, or other computation withrespect to detection results.

Some detector embodiments may be configured for visible spectrumdetection. In some embodiments, a visible spectrum detector may besufficient for dyes or dye-combinations having visible spectrumfluorescence responses. In other embodiments, detectors may beconfigured to operate in visible and non-visible portions of theelectro-optical spectrum, such as the infra-red, ultra-violet, ormillimeter wave spectra. In such embodiments, in addition to reading thevisible portion of a photo-responsive dye code written on a box or bagor other item, the detector can also be configured to detect thespecific response wavelengths associated with photo-excitation of thephoto-responsive dyes used in at least part of the printed code.Alternate embodiments may have multiple detectors or may includespectral filtering techniques or components (such as notch or band-passfilters). Detectors equipped with filters or other frequency bandspecific detection capabilities may be used to read embodiments of codesor article identifiers created with dyes that have overlapping responsefrequency bands, such as a first dye with a response between 550 and 600THz and a second dye with a response between 570 and 580 THz.

Embodiments of detectors may include focal plane arrays, linear scanningarrays, photodiodes, charge-coupled devices, multi-color detectordevices, or coupled monochrome detectors. Further embodiments mayinclude selective filtering such that a monochrome detector may effecttwo-color operation by restricting certain pixels of the detector toonly certain wavelengths or wavelength ranges. Yet further embodimentsmay include multiple emitter/detector combinations or variations such asa range-finding detector, a temperature-sensing detector, and acode-reading detector—all of which may be parts of a single detectordevice or element, or may be separate detector components associatedwith particular emitters. Further embodiments still may includesingle-emitter/single-detector embodiments configured to work with oneparticular photo-responsive dye or with multiple photo-responsive dyeshaving activation and response frequencies covered by the emitter anddetector, respectively. Yet further embodiments may include detectormodulation such that the detector is selectively or sequentiallyactivated to produce a modulated detection signal from an un-modulatedemitter signal or to work in concert with a particular emitter sequenceor modulation. Such embodiments may be configured to create detectionprofiles, sequences, or intensity gradients that can only beaccomplished by a combination of one or more particular photo-responsivedyes and particular emitter or detector modulation sequences.

The processor 1161 and memory 1151 embodiments shown in FIG. 1 a mayinclude any suitable data processing and storage technology, includingdigital signal processors, analog transistor cores, volatile datastorage (such as RAM or PROM), optical data storage, magnetic datastorage, and removable data storage portions. Processor 1161 embodimentsmay be configured to operate the emitter 1131 and detector 1141 based onprogram or operating parameters stored in memory 1151 or input via theinterface 1111. In some embodiments, the processor can control emitter1131 illumination sequence and/or pulse frequency according toparameters provided either through programming or user control and/orvia material-specific calibration steps (such as particular pulsemodulation frequencies associated with particular dyes or dyecombinations based on desired response profiles or information codingtechniques). Operation of the detector, such as integration or read-outtimes, detector modulation. The scan results acquired by the detectormay also be stored in memory 1151 and/or displayed via the interface1111 or passed to another system for further display or processing.

In some reader device embodiments, emitter and/or detector modulationmay be accomplished with a pulse modulator device or unit 1171 as shownin FIG. 1 b. Such a component may be integrated into an emitter ordetector assembly or may be a standalone component containing one ormore programmed and/or selectable modulation profiles oremission/detection sequences.

In the embodiment shown in FIG. 1 a, the photo-responsive code 1031 isprinted in two different dyes 1001, 1021 on a box 1011 that may be aninventory or storage item or a product for sale. In the embodimentshown, the two photo-responsive dyes have different excitationfrequencies but the same response frequency. Embodiments of dyes mayinclude ones that are responsive to ultra-violet, infra-red, laser,millimeter-wave, or polarized electro-optical radiation. Furtherembodiments may be responsive to specific wavelength and intensitycombinations of electro-optical radiation and/or specific polarizationtypes. Further embodiments may include anti-stokes fluorescent dyes,quantum-dot-bearing inks or other inks or dyes with photo-converting orphoto-emissive properties.

Single response frequency band embodiments may be used withsimultaneous, sequential, or modulated emission/detection approaches. Inan embodiment using simultaneous emission, both excitation frequenciesare simultaneously provided to the dye-bearing code and the response ofboth dyes is detected. Authentication or verification may then beaccomplished by comparing the detected response against an expectedresponse. In embodiments where the entire code is printed inphoto-responsive dyes, the entire code may be evaluated. In embodimentswhere only part of the code is printed in photo-responsive dyes (theremainder of the code being printed in ordinary ink—the term “ordinaryink” means any non-fluorescent ink, including inks and dyes not readilyvisible to the naked eye or otherwise not readily discernible ordistinguishable in the visible spectrum, such as infra-red orultra-violet dyes, or laser-readable inks), the photo-responsive part ofthe code may be compared or otherwise processed in conjunction withthose parts of the code that are not photo-responsive. This may beaccomplished using a hashing function or some other verification methodto ensure that the photo-responsive and non-photo-responsive codeportions are correctly associated or otherwise indicative of a validcode or article identifier.

An embodiment of such an article identifier is shown in FIG. 2 a. Theembodiment depicted uses an alpha-numeric code 1231 printed in twophoto-responsive dyes 1201, 1211—some numbers printed in the first dyeand some in the second—and an ordinary ink 1221. Although the depictedembodiment shows one of the photo-responsive code portions as ahexadecimal number, any numeric or alpha-numeric counting system may beemployed (including ones employing reader-based ascii conversion orsimilar methods of deriving numerical values from representationalcharacters or images) In the embodiment shown, the printed code is atleast partially visible to the naked eye so that a person using acode-reader device will know where to point the device. In asimultaneous illumination embodiment, an emitter may trigger responsefrom the first and second dyes 1201, 1211 and simultaneously read theresponses of both dyes as well as any non-photo-responsive codecomponents.

In a sequential illumination embodiment, one of the dyes 1201 may betriggered for response before the other dye 1211. The detection resultsof both responses may then be compared and evaluated to determinevalidity based on response spectral content, intensity, and time as wellas the data content of the response. Alternate embodiments may alsocompare the illuminated detection(s) to an either previously orsubsequently read image of the un-illuminated code. Other embodimentsmay employ photo-responsive dyes having different emission frequenciesbut the same excitation frequency. Such approaches may allow for thecreation of visually monochromatic codes that are in producing codeportions in different wavelengths. In yet other embodiments, a singlephoto-responsive dye may be used either alone or along with ordinaryinks.

In a modulated illumination embodiment, an emitter may provide aparticular sequence of illumination pulses to trigger the dyes in apredetermined response sequence, such as an alternating responsesequence or one meant to provoke varying response times. Alternateembodiments may also include simultaneous illumination with delayedresponse. Such embodiments may use dyes having delayed fluorescenceresponse in combination with dyes having either no delay or differentdelay. Embodiments of dyes may include substances such as dopedanthracene, europium tetracycline complex, C70 (fullerene), and othersubstances having delayed fluorescence response. In some embodimentssuch substances may be included in dyes having the same excitation andresponse frequency bands, but different fluorescence delays.Simultaneous illumination of an article identifier containing such dyesmay allow for sequential detection and validation of an identifier basedon both data content and delay between fluorescence responses ofidentifier components. Such delayed response embodiments may also becombined with sequential or modulated illumination approaches. Suchembodiments may include dyes having particular relaxation or recoverytimes between fluorescence responses such that illumination at aparticular modulation may trigger fluorescence response at a differentrate (i.e. response to only every other or every third pulse due torelaxation or recovery time of a dye between fluorescence responsecycles).

Embodiments using dyes with differing excitation frequencies,fluorescence response times, and/or relaxation cycles in combinationwith sequential, simultaneous, or modulation illumination and/ordetection may be useful for an article identification or codeauthentication system where a code or identifier is based on or containsinformation related to a function that accepts, as inputs, the portionswritten in the photo-responsive dyes, time-difference data, and/or rateof response vs. rate of illumination data. Such information may becompared or otherwise evaluated or subjected to mathematical operationssuch as hash functions that may or may not include information containedin any plainly visible portions of an embodiment of a code oridentifier. Such a “hide-in-plain-sight” solution may allow forauthentication of goods, vehicles, livestock, buildings, fortifications,or individuals without alerting potential counterfeiters or intruders orthieves that an authentication system is in place beyond the visibleserial number.

Further embodiments of such a code may include “spoofing features” thatmay appear to be part of the code but are there to mislead code-breakingor code-counterfeiting attempts. Such embodiments may include extraneouscharacters or image portions written in ordinary or photo-responsivedyes that are either outside the detection spectrum of a reader deviceor are otherwise selectively ignored during a code-reading operation.Such embodiments may also leverage delayed fluorescence aspects of somephoto-responsive dyes. A photo-responsive dye with an immediatefluorescence response 1201 may be combined with a photo responsive dyehaving delayed response 1211. In an embodiment where both dyes have thesame excitation and response frequency, detection may be delayed aspecified amount of time such that only the delayed-response dye is reador may be stopped after a specified amount of time such that only theimmediate response dye is read, with the other dye creating bogus datameant to confuse would-be counterfeiters or thieves.

A further embodiment of a spoofing code approach is depicted in FIG. 2b. In the embodiment shown, visible portions of a code or image 2021 maybe embedded within a larger image 2011, with the larger image 2011 andthe code-bearing or article identifier portion 2021 both having the samevisual appearance (in both color and texture). The larger image may becreated using a dye having a broad-spectrum response while thecode-bearing portion is created using a dye having a narrow-spectrumresponse contained in the broad-spectrum response dye. An example mayinclude a broad-spectrum dye with a response waveband of 660 to 690 nmand a narrow-spectrum dye with a response waveband of 680 to 670 nm. Adetector equipped with a notch filter would register a negative image ofthe code 2021 whereas an observer would, without the aid of specializedequipment, be unable to discern the presence of an embedded code in theimage even with an awareness of its photo-responsive properties.

In an alternate embodiment, a code dye 2010 having a delayed responsemay be utilized in conjunction with a spectrally identical dye havingeither no delay or a different delay. A modulated illumination approachmay be used to activate and then ‘drown out’ the code repeatedly. Insuch an embodiment a detector may eventually develop an image of thecode whereas the activation and drown-out time may be too rapid for ahuman observer to discern.

In further embodiments, the code symbols 2021 and the “substrate” image2011 can be printed in two different photo-responsive dyes that eitherhave different trigger wavelengths or different photo-responsewavelengths. A code reader of the type in FIGS. 1 a or 1 b may be usedto read both the immediately visible and photo-responsive portions ofthe code. Depending on how the reader is configured, the reading may besimultaneous, sequential, or some combination thereof (such as firstreading the visible and then reading both photo-responsive portions, orvice-versa).

Further embodiments of spoofing solutions may include an image, letter,or number printed partially in a photo-responsive dye and partially in avisually identical non-photo-responsive dye. In the embodiment shown inFIG. 2 c, an alpha-numeric sequence 2131 may be embedded within an image2031 or printed on a container or surface. A portion of this sequence2251 may be printed in an ordinary ink and a portion may be printed in aphoto-responsive dye 2231. In the embodiment depicted, half of thenumber “8” is printed in ordinary ink whereas the other half is printedin an ink carrying a photo-responsive dye. Although printed as “8S:D,”the photo-responsive portion of the code is actually “3S:D” (3 beinghalf of 8 from a visual standpoint). Other examples can includeembedding the letter i or 1 into a capital H or the number 4, orembedding an asterisk shape into a radiation symbol.

Alternate embodiments may combine different photo-responsive dyes havingspecific fluorescence/phosphorescence relaxation times, response delays,or response waveband overlaps. In delayed response or relaxation timeembodiments, an illumination pulse sequence with a specific pulsesequence, modulation profile, or modulation frequency (or frequencies)can be used to excite such materials into producing the desiredresponse. Relaxation phenomenon associated with suchfluorescent/phosphorescent materials may include or otherwise allow fortime delays that, when expected, can be leveraged to provide additionallabel-specific information and/or data. In some embodiments, expectedtime delay between excitation/relaxation cycles in a material may beleveraged against a pulse modulation sequence offset from the responseprofile of the material such that the temporal characteristics of thematerial response serve to authenticate a code or provide some or all ofa decoding key for information stored in or associated with the code. Inembodiments having spectral overlap, notch or band-pass filtering may beused to separate the ‘bogus’ photo-response from the desiredphoto-response. In either embodiment, the desired code or articleidentifier components may be embedded within valid-looking but partiallybogus codes, making the code more difficult to identify and extract.

Further variations of such an embodiment may include writing the code indyes that respond to photo-excitation in two visually indistinguishableshades of orange (or green, or mauve, or black, or any other suitablecolor or color combination) and having a scanner specifically calibratedto distinguish between the two shades (460 nm vs. 480 nm, for example).Further variations may include using day-glow inks (inks whoseexcitation frequencies are in the visible spectrum) to make thefluorescence response of the photo-responsive dyes more difficult todetect with the naked eye.

In yet another embodiment, shown in FIG. 2 d, a numeric or imagesequence (or a combination thereof) 2221 can be embedded in an image2211 or a pictographic sequence may be embedded in an alphanumericcharacter or code, or some variation thereof. The photo-responsiveproperties of the embedded code(s) 2001, 2323 may be configured suchthat some or all of the code has a broad-spectrum photo-response whereasother portions may have narrow-spectrum response or otherwise bevisually indistinguishable during broad-spectrum illumination. Part ofall of the embedded code 2221 may have the visual-spectrum color of itsassociated shape such that visual examination will not show the embeddedcode. In such embodiments a modulated or otherwise predeterminedillumination sequence may be required to generate broad-spectrumresponse followed by narrow spectrum response or narrow-spectrum colordetection and processing. Purely broad-spectrum illumination, even withthe required broad-spectrum frequency band necessary to activate part ofthe code 2001, may drown-out or otherwise fail to trigger the otherportions 2323, providing a further level of data security to delay andcomplicate unauthorized access or duplication attempts.

Alternate embodiments may employ visibly distinct embedded codes orpartially visible embedded codes such that a user or machine operating areader will have a reference point for reading the codes. In theembodiment shown 2221, the numeric sequence 2323 may be created by usingoff-setting circles of photo-responsive dye 2001 to create negativeimages of the numbers 2323. In alternate embodiments, positive imagescan be painted or a combination of positive and negative images can beused. In yet further embodiments, the “substrate” image 2211 may also beprinted in a photo-responsive dye. Embodiments of such a multi-dyesolution may include a background image 2211 responsive at 640 nm, anintermediate image 2001 responsive at 650 nm and an internal image 2323responsive at 660 nm, requiring sensitive spectral filtering to separateand analyze the code portions. Further embodiments may have a backgroundimage with no response delay or relaxation time, an intermediate imagewith sub-microsecond delay or relaxation time, and an internal imagewith multi-microsecond delay or relaxation time, requiring a specificemitter sequence or detection sequence to identify and analyze the codeportions.

Further embodiments may employ one or more visually multi-chromic dyeshaving photo-responsive properties as discussed above. Such embodimentsmay have a multi-colored code (such as an image) that, when exposed toparticular excitation frequencies, responds with a specific lightwavelength. Such embodiments may include a sequence of images or imageportions meant to be read or analyzed in a particular order. Exposure toa first excitation frequency causes a particular set of images or imageportions to respond, which are then read and processed as a group. Thesemay be added, subtracted, or otherwise compared against the visiblespectrum portion(s) of the image for decoding or authentication.Embodiments using multiple dyes or particular modulation sequences maycall for further exposure to subsequent excitation frequencies orfrequency modulations may cause subsequent sets of images or imageportions to respond. These may also be read as a group or may be somehowvisually added to or subtracted from the first image set or the visibleimage portions (or both) to generate a code or code portion.

One such embodiment is depicted in FIG. 2 e. In the embodiment shown,two overlapping images may create three distinct response areas. A firstimage containing a first photo-responsive dye 2111 may be overlappedwith a second image containing a second photo-responsive dye 2121. Theoverlapped area 2151 may, in an embodiment where the dyes share a commonexcitation frequency band, generate a combined or composite fluorescentresponse distinct from either the first or second dye. Such embodimentsmay be combined with image-based or alphanumeric article identifiers toprovide additional verification or detection data for a code or articleidentifier.

A further embodiment of an overlapped-image article identifier isdepicted in FIG. 2 f. In the embodiment depicted, an image of a camera2051 may include, either as part of the dyes and inks included in theimage or as invisible, photo-responsive dye components, image portions2511, 2521 made of photo-responsive inks or dyes (such as fluorescentdyes). The image portion can overlap at least partially and can bescanned and read either sequentially or simultaneously. For embodimentsusing dyes that have different response frequencies and/or responsedelays, simultaneous illumination may result in combined or hybridresponse from the overlapping portions. One dye may partially filter oraugment the response of the other—much like mixing or layering paintswould do for visible spectrum colors. Such attenuation, blending, orenhancement as a result of the overlap may also be used as acode-bearing component. In further embodiments, similar effects can beintroduced by leveraging the temporal aspect offluorescent/phosphorescent relaxation phenomenon, whereby incorrectlypulsed illumination will not resolve the proper code. In suchembodiments, dyes having different response delays or relaxation timesmay be fully or partially overlapped such that the different code orinformation portions contained in the dyes may only be resolved usingthe proper illumination pulse modulation profile. In some embodiments,this may allow for spectral shift during or resulting from illumination(i.e. a code may fluoresce green and then shift to blue or yellow ascertain portions begin responding later or cease fluorescing earlier).Further embodiments may include only one photo-responsive dye or mayinclude many photo-responsive dyes. Such embodiments may alsoincorporate the spoofing solutions discussed above.

A further embodiment may include an encoding system foroptically-readable media (including bar codes, punch cards, printedtext, cds, dvds, etc.). In some cases, the information itself may beprinted as a sequence of images that are at least partially written intwo or more such photo-responsive dyes. A specialized scanner may readthe printed images and their excitation response frequencies todetermine a decoding sequence and process that may recover code datastored therein. This may be useful for printed message where some of theprint is generated with a first dye having a first excitation frequencyand some generated with a second dye having a second excitationfrequency. The message itself may be encoded using a purely text-basedencoding in addition to the dye-based approach.

An alternate example may include an optically-readable disc or similarmedia (etched glass, etc.) having what looks like “cover art” that is infact an authentication code providing an access key that may be requiredto read or decode specific encoded portions of the data stored on themedia.

Further embodiments may employ seemingly mono-chromatic dyes included aspart of colored blocks on any suitable ink-bearing medium (paper, glass,metal, stone, fabric, skin, etc.). Such embodiments may have “hidden”visible codes composed of narrow-frequency dyes hidden in swaths ofbroader-spectrum paint. An example may include a limited editionlithograph where a section of the picture that is, say, a solid area ofblue, has an authentication code printed in one or more visuallyindistinguishable blue inks that are composed of only one particularshade of blue or that respond to photo-excitation with a particular,narrow frequency. A scanner with a series of narrow-band optical filterswould be required to distinguish the various shades of blue and read theauthentication code.

Yet further embodiments may employ overlapping layers ofphoto-responsive dyes having different excitation frequencies but thesame response frequency. Such an approach may be useful for embeddingcode fragments in visible media (such as a printed image or bar code ornumber) where the code generation process is sequence-driven. Exposingthe printed image to the first excitation frequency and then adding orsubtracting that response image from the one generated by the secondexcitation frequency in a particular sequence (such as doubling or fullyremoving the overlap portions, or considering only the fully overlappedportions) may add an additional level of protection to codes even incases where potential counterfeiters or thieves or intruders may knowthe required excitation frequencies to trigger the photo-responsive codeportions.

Yet further variations may employ approaches where the photo-responsivedyes are colorless and mixed with conventional inks or dyes. Suchapproaches may allow code sequences to be painted into portions ofvisible serial numbers. Such approaches may also allow fabrics ormaterials to be dyed with photo-responsive dyes or ink formulations asdescribed above. This may be especially useful for authenticatingcommonly-counterfeited merchandise such as clothing, shoes, andhandbags. A manufacturer or designer tag may have an embroidered ordyed-in serial number or authentication code having multiple invisible,photo-responsive portions that have either different response orexcitation frequencies as discussed previously. Such an embodiment isshown in FIG. 3. In the embodiment shown, a garment tag 3001 has anumeric code that may be printed, embroidered, or otherwise embedded inthe tag. The code may include photo-responsive portions of anembroidered logo or may include portions of lettering or images printedon the tag. In further embodiments, the code may be embedded in thefabric of the tag itself and unrelated to anything embroidered orprinted thereon. Tags according to such embodiments may be manufacturedby clothing companies, designers, or security specialty operations. Suchtags may be used to allow stores and consumers to verity theauthenticity of a particular brand or item of clothing. For embroideredor printed embodiments, thread or ink having the proper photo-responsivedyes may be provided to clothing manufacturers for use or the tags maybe separately produced.

Yet further embodiments may employ materials having inherent physicalproperties associated with or similar to the spectral and/orfluorescence properties of a dye such that a code may be generated basedon the interaction between the intrinsic spectral properties of amaterial and those of a photo-responsive dye disposed or otherwisedeposited thereon or therein.

Such codes may be used as inventory tracking codes associated withparticular items or livestock or the like. In such cases, even a stolenor perfectly forged tag may be discovered because it is not associatedwith the particular thing that its code indicates it should be. In yetfurther embodiments, watches may also use such authenticating dyes aspart of movements or watch faces so that counterfeits can bedistinguished from genuine articles by a quick visual scan of thedevice.

Further embodiments still may combine coded tags or identifiers with areader or scanner device which communicates with a central database. Insuch an embodiment a reader device may, upon scanning a particular code,associate that code with a scan location. An embodiment of such a readeris depicted in FIG. 4. In the embodiment shown, a reader 1101 isequipped with a GPS data unit 1191 and a communication interface 1181.The GPS data unit may be used for GPS position acquisition to establishtime and location coordinates associated with a particular scanningoperation. Alternate embodiments may replace or augment such a GPS dataunit with a clock and a selectable or preset location setting. Suchembodiments may be used in settings such as a warehouse or distributioncenter where the reader devices are meant to operate only within aparticular warehouse or center or otherwise configured to acquirelocation data based on the warehouse or distribution center. One suchembodiment may include a system where a reader synchronizes itself via alocal network or bluetooth connection with an inventory database serverlocated in or configured for access from the warehouse. Suchsynchronization may be accomplished through a communication interface1181 that may be a radio-frequency transmitter, an optical data transferunit, or a data jack configured for a hard-wired connection, or somecombination thereof. In some embodiments, the communication interfacemay be part of the power or charging architecture for cordless,battery-powered readers. In other embodiments, the communicationinterface may be part of the user interface 1111 and/or the locationdata unit 1191 or otherwise integrated with one or both of those units.

In such a solution a scan would associate a time and location with aparticular inventory item and provide such tracking or logistical datato retailers or consumers of the inventory item. A counterfeit or stolenitem scanned at a subsequent location may then have its scan locationand time compared with the last known scan location and time for the‘valid’ tag. If an item reads as being in a physically impossiblelocation (i.e. scan 1 on Monday in Bogota, scan 2 on Tuesday in Beijing)the item is flagged as possibly counterfeit or otherwise noted forfurther investigation. If an item previously marked as stolen orotherwise in an improper location is scanned (i.e. goods marked asdestined for Dallas show up in Moscow), the scanning party may bealerted and further corrective action may be indicated.

Alternate embodiments may employ a hidden key solution. In suchembodiments, a code or code portion disposed on an article and read witha reader must be compared or otherwise validated or examined inconjunction with key or code information stored elsewhere andunobtainable by only examining the code on the article. Such embodimentsmay include alphanumeric, image-based, or composite code sequences wherea decoding or completing key or set of key data is stored in orotherwise provided to a reader device in conjunction with a code-readingoperation.

In one embodiment, a reader device may contain an authentication code orimage or data set such that the code read from the article may only beauthenticated by a reader having the proper authentication information.An embodiment of this type may include a solution where a readerreceives a “heartbeat” signal from an associated location, such as awarehouse, and that heartbeat signal contains the authenticationinformation required to properly read article identifiers.

In one embodiment, shown in FIG. 5, the communication interface 1181 ofa reader device may include a radio-frequency unit such as a Bluetoothdevice that associates the reader with a key or code or heartbeat signalgeneration server or system 5101 in a warehouse or other code-readingfacility either through direct connection 5111 or via a data network5201. The associated reader may then receive decoding information fromthe associated system 5101 and use that data to read and verify ordecode an embodiment of a dye-based code. In some embodiments,particular facilities may have one or more particular decoding orverification codes or keys. Such facility and time-specific coding maybe considered when generating or associating article identifiers suchthat a read article identifier may only be decoded or authenticatedusing decoding information associated with a particular time and/orplace. Codes indicating merchandise intended for San Francisco, forinstance, would not be properly read by a warehouse in Buenos Aires. Inanother example, article identifiers generated or created in April mayonly be read as valid during an expected shipping or transit period inMay based on such time and location based decoding information.

In another embodiment, the communication interface 1181 may be acellular communication device, an optical communication device, or someother information exchange unit that receives the additional decodinginformation or transmits scanned code information for decoding orverification at a remote location where the decoding information isstored. Further embodiments may include a system where a reader issynchronized with a decoding information server or system that routinelyupdates and propagates new decoding information and, in some variations,associated decoding validation/authentication criteria, such that aparticular piece of decoding information is only usable during aparticular time period.

Further embodiments may be configured using public/private key pairssuch that a code or article identifier includes, in its detectableproperties, a public key that can only be read or authenticated incombination with a private key accessed by, provided to, or otherwisestored in the reader device. Such a private key may be issued by akey-issuing system associated with the reader or may be provided to areader user who must input or otherwise provide the key data to thereader during use via the user interface 1111. In yet furtherembodiments, a private key may be associated with an initiation orinitialization operation associated with the reader. Such embodimentsmay require that a reader be provided with the private key as part ofits activation or power-on process.

In yet further embodiments, a reader device may also generate decodinginformation for subsequent reading or scanning operations. In one suchembodiment a detector 1131 may capture an image during a code-readingoperation or may otherwise store a previously or subsequently capturedimage to be associated with a particular code reading operation. Thiscaptured image, or a data string based on the captured image, may thenbe transmitted, via the communication interface 1181 to the decodingdata provision system for use or reference in a subsequent readingoperation.

In yet further embodiments, a hidden-code style reader may have anon-associated operation mode where the code and component portionsassociated with the receipt, use, and/or generation of additionaldecoding data are de-activated and only a partial authentication orverification is performed during non-associated or otherwisenon-decoding-data-based code reading. In some embodiments, attempts toactivate or operate the decoding-data-based portions of such a readerwhile it is in a non-associated mode may trigger data or hardwareanti-tamper measures such as information deletion, deliberate deviceoverheating, or intentional overload of particular components.

Further variations of such approaches may also be used in combinationwith any of the above-described code printing and analysis techniques,or with any variations thereon. The invention being thus described, itwill be obvious that the same may be varied in many ways. Suchvariations are not to be regarded as departure from the spirit and scopeof the invention, and all such modifications as would be obvious to oneskilled in the art are intended to be included within the scope of thefollowing claims.

The invention claimed is:
 1. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component including a second fluorescent dye having a second excitation frequency band and a second response frequency band; where the response frequency band of the second dye includes the response frequency band of the first dye; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first dye has a fluorescence response delay of one micro-second or greater.
 2. The article identifier of claim 1, where the first and second dye have substantially identical spectral characteristics when not fluorescing.
 3. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component including a second fluorescent dye having a second excitation frequency band and a second response frequency band; where the response frequency band of the second dye includes the response frequency band of the first dye; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first dye has a post-fluorescence relaxation time greater than that of the second dye.
 4. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component including a second fluorescent dye having a second excitation frequency band and a second response frequency band; where the response frequency band of the second dye includes the response frequency band of the first dye; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first dye has a fluorescence response delay greater than that of the second dye.
 5. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component including a second fluorescent dye having a second excitation frequency band and a second response frequency band; where the response frequency band of the second dye includes the response frequency band of the first dye; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first and second identifier components include mathematically related information-bearing portions.
 6. The article identifier of claim 5, where the first identifier component is an image or alpha-numeric string embedded within the second identifier component.
 7. The article identifier of claim 5, where the response frequency band of the first dye is the same as the response frequency band of the second dye.
 8. The article identifier of claim 5, where the information-bearing portion of the identifier is at least partially alpha-numeric.
 9. The article identifier of claim 5, where the first and second dye have the same excitation frequency band.
 10. The article identifier of claim 5, where the first and second identifiers are part of information printed or embroidered on a garment tag.
 11. The article identifier of claim 5, the identifier further comprising a third identifier component including a third fluorescent dye having a third excitation frequency band and a third response frequency band.
 12. The article identifier of claim 5, where the information bearing portion is at least partially represented by an ordinary ink.
 13. The article identifier of claim 5, where at least one excitation frequency band includes infra-red wavelengths.
 14. The article identifier of claim 5, where the second response frequency band includes infra-red wavelengths.
 15. The article identifier of claim 5, the identifier further including a third identifier component created by combining or overlapping the first and second components.
 16. The article identifier of claim 5, where the identifier is a multi-layered image and where at least one image layer includes the first identifier component and at least one other image layer includes the second identifier component.
 17. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component having a second excitation frequency band and a second response frequency band; where at least the first and second response frequency bands or the first and second excitation frequency bands are substantially the same; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first dye has a fluorescence response delay of one micro-second or greater.
 18. The article identifier of claim 17, where the first and second identifier components have substantially identical spectral characteristics when not fluorescing.
 19. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component having a second excitation frequency band and a second response frequency band; where at least the first and second response frequency bands or the first and second excitation frequency bands are substantially the same; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; where the second identifier component includes a second dye having the same excitation frequency band as the first dye; and where the first dye has a post-fluorescence relaxation time greater than that of the second dye.
 20. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component having a second excitation frequency band and a second response frequency band; where at least the first and second response frequency bands or the first and second excitation frequency bands are substantially the same; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; where the second identifier component includes a second dye having the same excitation frequency band as the first dye; and where the first dye has a fluorescence response delay greater than that of the second dye.
 21. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component including a first fluorescent dye having a first excitation frequency band and a first response frequency band; a second identifier component having a second excitation frequency band and a second response frequency band; where at least the first and second response frequency bands or the first and second excitation frequency bands are substantially the same; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first and second identifier components include mathematically related information-bearing portions.
 22. The article identifier of claim 21, where the first identifier component is an image or alpha-numeric string embedded within the second identifier component.
 23. The article identifier of claim 21, where the response frequency band of the first dye is the same as the response frequency band of the second identifier component.
 24. The article identifier of claim 21, where the information-bearing portion of the identifier is at least partially alpha-numeric.
 25. The article identifier of claim 21, where the second identifier component includes a second dye having the same excitation frequency band as the first dye.
 26. The article identifier of claim 21, where the first and second identifiers are part of information printed or embroidered on a garment tag.
 27. The article identifier of claim 21, the identifier further comprising a third identifier component including a third fluorescent dye having a third excitation frequency band and a third response frequency band.
 28. The article identifier of claim 21, where the information bearing portion is at least partially represented by an ordinary ink.
 29. The article identifier of claim 21, where at least one excitation frequency band includes infra-red wavelengths.
 30. The article identifier of claim 21, where the second response frequency band includes infra-red wavelengths.
 31. The article identifier of claim 21, the identifier further including a third identifier component created by combining or overlapping the first and second components.
 32. The article identifier of claim 21, where the identifier is a multi-layered image and where at least one image layer includes the first identifier component and at least one other image layer includes the second identifier component.
 33. The article identifier of claim 21, where the second identifier component includes a second fluorescent dye.
 34. An article identifier identifying at least a characteristic of an article, the identifier comprising: a first identifier component having a first excitation frequency band and a first response frequency band; a second identifier component having a second excitation frequency band and a second response frequency band; where at least the first and second response frequency bands or the first and second excitation frequency bands are substantially the same; and where a property of excitation or response of the first component is different from a corresponding property of the second component and at least part of the identified characteristic is represented by this difference between the properties of the components; and where the first and second identifier components include mathematically related information-bearing portions. 